1. Field of the Invention
The present invention relates to communication networks and, more particularly, to a method and system for communicating data from wireline terminals to mobile terminals.
2. Background of the Art
In telecommunications networks, a wireline directory number (DN) is associated with a fixed geographic location and is served by a single wireline switch. A wireless DN, however, is associated with multiple geographic locations and is served by any one of a number of wireless switches depending on the specific geographic location of an associated wireless device at the time a call is made. This portability of a wireless DN is one of the basic attributes of wireless telephony.
A pair of home location register and visited location register in a telecommunications network provides seamless roaming when a call is placed to or from a wireless DN. A home location register is associated with a home wireless switch where all incoming calls to a wireless DN are first directed. A wireless device associated with a wireless DN is located within its home area when the wireless device can directly communicate with its associated home wireless switch (i.e., the wireless device is located in a geographical area served by the home wireless switch).
A visited location register is associated with a wireless switch that serves a wireless device when the wireless device is outside of its home area. A wireless device associated with a wireless DN is outside of its home area (or roams) when the wireless device cannot directly communicate with its associated home wireless switch and instead communicates with another wireless switch (hereinafter referred to “visited wireless switch”).
One problem with the present telecommunication networks is that two connections must be established when a call is placed to a wireless DN whose associated wireless device is outside of its home area. In such instances, the telecommunications network must establish a first connection to the home wireless switch associated with the wireless DN. The home wireless switch then must establish a second connection to a visited wireless switch serving the wireless DN.
As an illustration, consider data communication applications in the trucking and postal industries. These industries often use complex data communication networks for controlling and monitoring from fixed locations the activities of field personnel who are mobile and are geographically dispersed over a wide area. These data communication networks typically use conventional telecommunications networks for establishing communication between wireline data processing devices, such as desk top computers located in centralized offices, and wireless data processing devices, such as mobile terminals used by field personnel.
FIG. 1 shows a block diagram of one such conventional telecommunications network 100. Telecommunications network 100 comprises a wireline switch 110, a home wireless switch 120, a home location register 130, a signal transfer point (STP) 135, a visited location register 140, a visited wireless switch 150, a wireline terminal 155, such as a desktop personal computer, antenna 170, wireless modems 175l-175K, and mobile terminals 178l-178K. Wireline terminal 155 establishes communication with mobile terminals 178l-178K via wireless modems 175l-175K, respectively.
To establish communication with one of mobile terminals 178l-178K, for example mobile terminal 178l, wireline terminal 155 executes a dialup program, such as the Microsoft Dialer software developed by Microsoft. The dialup program initiates a call request 180a by dialing the wireless DN associated with wireless modem 175l. When wireline switch 110 receives call request 180a, wireline switch 110 establishes a first connection 180b via a Public Switched Telephone Network (PSTN) 160 to home wireless switch 120, the home switch associated with the dialed wireless DN.
Home wireless switch 120 sends an “Interim Standard 41” (IS-41) RouteRequest message 180c to its associated home location register 130, requesting the current location of wireless modem 175l. The ANSI-41 standard is described in “Radio Telecommunications Intersystem Operations,” ANSI/TIA/EIA/41-D-1997, which is incorporated herein by reference. The IS41 standard describes the communication protocol between home wireless switch 120, home location register 130, visited location register 140, and visited wireless switch 150 in telecommunications network 100.
If wireless modem 1751 is outside of its home area as shown in FIG. 1, home location register 130 then identifies the visited location register with which wireless modem 1751 last registered, for example visited location register 140, and sends an IS-41 RouteRequest message 180d via STP 135 to visited location register 140.
Visited location register 140 forwards the RouteRequest message 180d to its associated visited wireless switch 150, requesting a route to wireless modem 175l. Visited wireless switch 150 computes a temporary local directory number (TLDN), which is used to establish incoming calls to wireless modem 175l when wireless modem 175l is served by visited wireless switch 150. Visited wireless switch 150 then returns the TLDN to visited location register 140 in an IS-41 message 180e. Visited location register 150 then sends via STP 135 to home location register 130 an IS-41 RouteRequest response message 180f that includes the TLDN.
Home location register 130 forwards the RouteRequest response message 180f to home wireless switch 120. Based on the TLDN in the RouteRequest response message 180f received from home location register 130, home wireless switch 130 then establishes a second connection 180g to visited wireless switch 150. Visited wireless switch 150 then sends a ring signal to wireless modem 175l. When wireless modem 175l receives the ring signal, wireless modem 175l notifies a dialup program running on mobile terminal 178l, such as the Microsoft Dialer software developed by Microsoft and, waits for a response. When the dialup program responds, wireless modem 175l sends an answer signal via visited wireless switch 150 to wireline terminal 155, thus establishing a call between mobile terminal 178l and wireline terminal 155. Accordingly, telecommunications network 100 must establish two separate connections 180b and 180g to establish communication between wireline terminal 155 and mobile terminal 178l when mobile terminal 178l resides outside of its home area.